Surge arrestor

ABSTRACT

A surge arrestor comprising a flat ceramic substrate having a centrally disposed notch formed in the upper surface thereof. First and second electrodes are provided on the upper surface of the substrate and extend from opposite sides of the notch to the outer ends of the ceramic substrate. First and second leads are secured to the outer ends of the first and second electrodes respectively. A glass cover is secured to the upper surface of the substrate material between the electrodes and extends over the notch to define a spark gap compartment. The spark gap compartment is filled with a suitable radio-active gas such as Kr-85 and argon. Modified forms of the arrestor are also disclosed having various spark gap configurations.

[ 51 Aug. 19, 1975 3.6545 ll 4/l972 3l7/67 i 1 SURGE ARRESTOR Inventor: Herman R. Person, Columbus,

Nebr.

Primary Examiner-J. D. Miller Assistant E.\'mn1'ner-Patrick R. Salce Assigneei Dale Electronics, Inc, Columbus. Attorney. Agent, or FirmZarley, McKee. Thomte &

Nebr. Voorhees [22] Filed: Apr. 26, 1973 [2]} Appl. No.: 354,483

[57] ABSTRACT A surge arrestor comprising a flat ceramic substrate having a centrally disposed notch formed in the upper surface thereof. First and second electrodes are provided on the upper surface of the substrate and extend from opposite sides of the notch to the outer ends of the ceramic substrate. First and second leads are secured to the outer ends of the first and second electrodes respectively. A glass cover is secured to the upper surface of the substrate material between the electrodes and extends over the notch to define a [Sol References Cited UNITED STATES PATENTS spark gap compartment. The spark gap compartment is filled with a suitable radioactive gas such as Kr-85 3 7 and argon. Modified forms of the arrestor are also dis- 313/217 closed having various spark gap configurations.

3|7/7l Carroll, Jr. et al. 3 3/325 Schultz et al.

W n e P KS 467 6667 9999 HHHH A1741; 5077b 6868 9U64 So o ,2 3333 I3 Claims 8 Drawing Figures SURGE ARRESTOR BACKGROUND OF THE INVENTION This invention relates to a surge arrestor and more particularly to a surge arrestor which is substantially flat and which occupies a minimum amount of space. Conventional spark arrestors are ordinarily tubular in shape and do not easily lend themselves to automatic production methods. Additionally. the tubular surge arrestors of the prior art are fairly large and are not easily installed on printed circuit boards. Additionally, the surge arrestors of the prior art have a shunt capacitance of approximately 2pf.

Therefore, it is a principal object of the invention to provide an improved surge arrestor.

A further object of the invention is to provide a surge arrestor which may be constructed by using thick film technology.

A further object of the invention is to provide a surge arrestor which may be produced with automated equipment.

A further object of the invention is to provide a surge arrestor which may be fabricated from inexpensive materials.

A further object of the invention is to provide a surge arrestor which is substantially flat to enable it to be employed on printed circuit boards.

A further object of the invention is to provide a surge arrestor which has an extremely small shunt capacitance.

A further object of the invention is to provide a surge arrestor which may be employed in high frequency circuits without disrupting the characteristics of the circuits.

A further object of the invention is to provide a surge arrestor having improved operating characteristics.

A further object of the invention is to provide a surge arrestor having a glass cover disposed over the spark gap to enable the interior of the surge arrestor to be inspected.

A further object of the invention is to provide a surge arrestor which is durable in use.

These and other objects will be apparent to those skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS This invention consists in the construction, arrangements and combination of the various parts of the device, whereby the objects contemplated are attained as hereinafter more fully set forth, specifically pointed out in the claims, and illustrated in the accompanying drawings, in which:

FIG. 1 is a top perspective view of the surge arrestor of this invention:

FIG. 2 is an exploded perspective view of the surge arrestor of FIG. I:

FIG. 3 is a sectional view taken on lines 3 3 of FIG. 1:

FIG. 4 is an exploded perspective view of a modified form of the arrestor:

FIG. 5 is a sectional view taken on lines 5 5 of FIG. 4:

FIG. 6 is a bottom view of the arrestor of FIG. 5 as seen on lines 6 6 of FIG. 5:

FIG. 7 is an exploded perspective view of another form of the arrestor; and

FIG. 8 is a top view of a still farther modified form of the arrestor with the glass cover removed therefrom to more fully illustrate the invention:

DESCRIPTION OF THE PREFERRED EMBODIMENT The surge arrestor of FIGS. 1, 2 and 3 is referred to generally by the reference numeral 10. Arrestor 10 comprises a flat ceramic substrate material 12 having a bottom surface 14, top surface 16, opposite ends 18 and 20, and opposite sides 22 and 24.

The numeral 26 refers to a rectangular spark gap notch which is formed in the central area of substrate material 12 and which has it longitudinal axis disposed transversely to the longitudinal axis of the substrate material 12. The numeral 28 refers to an electrode which is screen printed on the top surface of substrate material 12 and which extends towards end 18 as seen in FIG. 2. The outer end of electrode 28 is provided with a pad portion 30. An electrode 32 is screen printed on the upper surface of substrate material 12 and extends towards the end 20 as illustrated in FIG. 2. Electrode 32 is provided with a pad portion 34 at its outer end. As seen in FIG. 2, the inner ends of the electrodes 28 and 32 terminate on opposite sides of the notch 26.

The numeral 36 refers to a screen printed seal material which is provided on the upper surface 16 of substrate material 12 as depicted in FIG. 2. It can be seen in FIG. 2 that the opposite ends of the seal material 36 are positioned inwardly of the pad portions 30 and 34. A gas hole 38 extends through the substrate material 12 as illustrated in FIG. 3. The gas hole 38 is formed in the substrate material 12 prior to the electrode material being screen printed on the substrate material 12 so that the electrode material will flow downwardly into the hole 38 to be deposited on the walls defining the hole 38. The numeral 40 refers to a soft solder plug which is installed in the lower end of the gas hole as will be explained in more detail hereinafter.

Tin plated copper wires 42 and 44 are soldered to the pad portions 30 and 34 respectively and would be connected to the circuit in which the arrestor is installed. A transparent glass cover 46 is secured to the upper surface 16 of substrate material 12 by means of the screen printed seal material 36.

The method of assembling the arrestor 10 is as fol lows. The notch 26 is formed in the ceramic substrate material 12 and the hole 38 formed in the material 12 if the hole has not been previously formed. The electrodes 28 and 32 are screen printed on upper surface 16 and would be comprised of a thick film ink or other suitable material. The seal material 36 is then screen printed on the upper surface 16. The seal material 36 would preferably be comprised of a glass frit material mixed with an oil base paint. Seal material would also be provided on the underside of the periphery 48 of cover 46. The cover 46 is then placed onto the seal material 36 and the surge arrestor placed in an oven having a temperature of approximately 450 to 480C to seal the cover 46 to the substrate material 12.

The leads 42 and 44 are then soldered to the pad portions 30 and 34. The surge arrestor is then placed in a vacuum chamber so that the compartment area 50 is evacuated. The compartment area 50 is then filled with an inert gas containing a radio-active isotope or the like. The soft solder plug 40 is then positioned in the hole 38 to seal the compartment area 50.

In operation, the surge arrestor 10 would be connected to any circuit requiring an arrestor. If a surge of predetermined magnitude should be experienced by the circuit, an arc will occur between the electrodes 28 and 32 in the spark gap notch 26 rather than on the surface of the substrate material 12. The shunt capacitance between the electrodes is very low which permits it to be used in high frequency circuits such as cable television or the like. The low shunt capacitance is provided because only small areas of adjacent electrodes confront each other. Prior art surge arrestors have a shunt capacitance of 2 pf whereas the surge arrestor 10 would have a shunt capacitance of less than I pf. This means that the surge arrestor It) could be used in low level circuits where frequency is up to 1,000 Hz.

The flat construction of the arrestor permits it to be used on printed circuit boards since it occupies very little space. The major advantage of the surge arrestor 10 is that it can be produced by using thick film technology which means that it can be made on automatic equipment and with inexpensive materials. The tubular prior art surge arrestors do not easily lend themselves to automated means. The transparent glass cover 46 permits the interior of the arrestor to be visually inspected to determine if the arrestor has experienced damage to its components. The flat construction of the surge arrestor allows several arrestors to be constructed on a single flat sheet of substrate material with the material then being broken along break lines to provide the individual surge arrestors. Thus it can be seen that the surge arrestor of FIGS. 1, 2 and 3 accomplishes at least all of its stated objectives.

The numeral It) refers to a modified form of the ar- 3 restor in FIGS. 4, and 6. A flat ceramic substrate material 12' has a spark gap notch 52 formed in the cen tral upper surface thereof as seen in FIG. 4. Notch 52 comprises a rectangular portion 54 and a wedge shaped portion 56. Electrode 58 is screen printed on the upper surface of the substrate material 12 and has its inner end communicating with the notch 52. Electrode 60 is also screen printed on substrate material 12 on the opposite side of the notch 52 and extends towards the other end of the arrestor as seen in FIG. 4. A gas hole 62 extends through the substrate material 12'. It can be seen that the material of the electrode 62 extends downwardly through the hole 62 to be in electrical contact with the electrode 64 which is screen printed on the bottom of the substrate material 12'. Electrode 64 comprises a pad portion 66 to which a lead 68 is soldered. Lead 70 is soldered to the pad portion 72 of electrode 58. Electrode 64 is screen printed on the bottom of the substrate material 12 so as to define a coil portion 74. The gas hole 52 is sealed with a soft solder plug 76 after the compartment area 78 beneath the glass cover 80 has been evacuated and filled with the inert gas. The arrestor I0 is assembled in substantially an identical manner to arrestor [0. In operation, the leads 68 and 70 are connected in series with the spark gap notch 52. The arrangement of the coil 74 is such that the arc in the spark gap notch 52 will be blown into the open wedge portion 56 to direct the are away from the inner ends of the electrodes to prevent the electrode material from burning which increases the life of the unit. The arrestor functions substantially identical to arrestor 10 except that arrestor I0 is provided with a magnetic field producing coil which is connected in series with the spark gap to blow the arc into the open wedge as previously described.

The numeral 10" refers to a surge arrestor in FIG. 7 which is substantially identical to the surge arrestors 10 and 1 except that the surge arrestor 10" is a three terminal surge arrestor. As seen in FIG. 7, screen printed electrodes 82, 84 and 86 are disposed adjacent a Y- shaped notch or groove 88 formed in the substrate material. The leads 88, 90 and 92 would be soldered to the pad portions 94, 96 and 98 of electrodes 82, 84 and 86 respectively. The glass cover 100 is installed on the device as in the previously described arrestors.

In FIG. 8, the numeral 10" refers to a surge arrestor which is of the three terminal type and which has a blow out coil connected in series with one of the terminals. A blow out coil similar to that shown in FIG. 6 would be provided on the underside of the substance material and would be in electrical contact with the screen printed electrode I02 through the gas hole 104. The inner ends of screen printed electrodes I02. I06 and 108 communicate with a Y-shaped or fan-shaped spark gap notch 110 formed in the substrate material. Notch I10 includes two fan portions 112 and I14 as seen in FIG. 8. If an arc should occur in the spark gap notch 110, the magnetic field created by the blow out coil on the underside of the substrate material will cause the arc to be blown outwardly into the portions 112 and 114 to prevent the electrode material from being burned.

Thus it can be seen that an arrestor has been provided which accomplishes at least all of its stated objectives.

I claim:

I. A surge arrestor comprising,

a flat substrate material having a top surface and opposite ends. said substrate material having a spark gap notch formed in its top surface, a first electrode on said top surface extending from one side of said notch towards one end of said substrate material,

a second electrode on said top surface extending from the other side of said notch towards the other end of said substrate material.

first and second leads secured to said first and second electrodes respectively.

and a sealed cover means secured to said top surface extending over said notch. said cover means being secured at its periphery to said top surface and being positioned between said first and second leads.

2. The surge arrestor of claim 1 wherein said cover means is comprised of a transparent material.

3. The surge arrestor of claim 1 wherein said cover means is comprised of a transparent glass material.

4. The surge arrestor of claim 1 wherein said cover means has a dome portion which is spaced above the top surface of said substrate material to define a compartment area.

5. The surge arrestor of claim 4 wherein an inert gas is confined in said compartment area.

6. The surge arrestor of claim I wherein said electrodes are screen printed on said substrate material.

7. The surge arrestor of claim 1 wherein a seal material is screen printed on said top surface of said substrate material. said seal material sealably engaging the periphery of said cover means.

8. The surge arrestor of claim 1 wherein a third electrode is positioned on said top surface and extends from said notch. said notch being Y-shaped.

9. A surge arrestor comprising,

a flat substrate material having a top surface and op- 5 posite ends, said substrate material having a spark gap notch formed in its top surface, a first electrode on said top surface extending from one side of said notch towards one end of said substrate material,

a second electrode on said top surface extending from the other side of said notch towards the other end of said substrate material,

first and second leads secured to said first and second electrodes respectively,

a sealed cover means secured to said top surface extending over said notch.

said substrate material having an opening formed therein and extending therethrough, one end of said opening communicating with the interior of said cover means, said opening being provided to supply an inert gas material into the interior of said cover means, and a solder plug means in the other end of said opening to seal said opening.

10. The surge arrestor of claim 9 wherein said electrodes comprise a screen printed electrode material, at least some of said electrode material extending downwardly through said opening, said solder plug means being secured to the electrode material in said opening.

11. A surge arrestor comprising,

a flat substrate material having top and bottom surfaces opposite ends and opposite sides,

said substrate material having a spark gap notch formed in its top surface,

a first electrode on said top surface extending from one side of said notch towards one end of said substrate material,

a second electrode on said top surface extending from the other side of said notch towards the other end of said substrate material,

said substrate material having an opening formed therein and extending therethrough,

said second electrode extending downwardly through said opening to said bottom surface, said second electrode extending outwardly on said bottom surface towards said other end,

a first lead secured to said first electrode,

a second lead secured to said second electrode on said bottom surface adjacent said other end,

a sealed cover means secured to said top surface extending over said notch,

and means sealing said opening.

12. The surge arrestor of claim 11 wherein said notch comprises a rectangular portion and a wedge shaped portion at one end thereof, said second electrode on said bottom surface defining a blow-out coil so that a spark occurring in said rectangular portion will be blown into said wedge shaped portion away from said electrodes.

13. The surge arrestor of claim 11 wherein said notch comprises a rectangular portion having a pair of diverging notch portions extending from one end thereof, a third electrode on said top surface having one end positioned adjacent said notch between said diverging notch portions and extending towards one of said sides of said substrate material, said second electrode on said bottom surface defining a blow-out coil so that a spark occurring in said rectangular portion will be blown into said diverging notch portions. 

1. A surge arrestor comprising, a flat substrate material having a top surface and opposite ends, said substrate material having a spark gap notch formed in its top surface, a first electrode on said top surface extending from one side of said notch towards one end of said substrate material, a second electrode on said top surface extending from the other side of said notch towards the other end of said substrate material, first and second leads secured to said first and second electrodes respectively, and a sealed cover means secured to said top surface extending over said notch, said cover means being secured at its periphery to said top surface and being positioned between said first and second leads.
 2. The surge arrestor of claim 1 wherein said cover means is comprised of a transparent material.
 3. The surge arrestor of claim 1 wherein said cover means is comprised of a transparent glass material.
 4. The surge arrestor of claim 1 wherein said cover means has a dome portion which is spaced above the top surface of said substrate material to define a compartment area.
 5. The surge arrestor of claim 4 wherein an inert gas is confined in said compartment area.
 6. The surge arrestor of claim 1 wherein said electrodes are screen printed on said substrate material.
 7. The surge arrestor of claim 1 wherein a seal material is screen printed on said top surface of said substrate material, said seal material sealably engaging the periphery of said cover means.
 8. The surge arrestor of claim 1 wherein a third electrode is positioned on said top surface and extends from said notch, said notch being Y-shaped.
 9. A surge arrestor comprising, a flat substrate material having a top surface and opposite ends, said substrate material having a spark gap notch formed in its top surface, a first electrode on said top surface extending from one side of said notch towards one end of said substrate material, a second electrode on said top surface extending from the other side of said notch towards the other end of said substrate material, first and second leads secured to said first and second electrodes respectively, a sealed cover means secured to said top surface extending over said notch, said substrate material having an opening formed therein and extending therethrough, one end of said opening communicating with the interior of said cover means, said opening being provided to supply an inert gas material into the interior of said cover means, and a solder plug means in the other end of said opening to seal said opening.
 10. The surge arrestor of claim 9 wherein said electrodes comprise a screen printed electrode material, at least some of said electrode material extending downwardly through said opening, said solder plug means being secured to the electrode material in said opening.
 11. A surge arrestor comprising, a flat substrate material having top and bottom surfaces opposite ends and opposite sides, said substrate material having a spark gap notch formed in its top surface, a first electrode on said top surface extending from one side of said notch towards one end of said substrate material, a second electrode on said top surface extending from the other side of said notch towards the other end of said substrate material, said substrate material having an opening formed therein and extending therethrough, said second electrode extending downwardly through said opening to said bottom surface, said second electrode extending outwardly on said bottom surface towards said other end, a first lead secured to said first electrode, a second lead secured to said second electrode on said bottom surface adjacent said other end, a sealed cover means secured to said top surface extending over said notch, and means sealing said opening.
 12. The surge arrestor of claim 11 wherein said notch comprises a rectangular portion and a wedge shaped portion at one end thereof, said second electrode on said bottom surface defining a blow-out coil so that a spark occurring in said rectangular portion will be blown into said wedge shaped portion away from said electrodes.
 13. The surge arrestor of claim 11 wherein said notch comprises a rectangular portion having a pair of diverging notch portions extending from one end thereof, a third electrode on said top surface having one end positioned adjacent said notch between said diverging notch portions and extending towards one of said sides of said substrate material, said second electrode on said bottom surface defining a blow-out coil so that a spark occurring in said rectangular portion will be blown into said diverging notch portions. 